Examination of internal body substances, gases or solid particles in the digestive system or the gastrointestinal tract in the human or animal body provides essential medical information for diagnosing and treatment. Examination of a sample of the gastric fluid of a patient provides important information of pH, acid contents, abdominal enzyme activity as well as information for diagnosing gastric ulcer and gastritis, cancer and tumour diseases, etc. A gastroscopic examination gives the physician who is treating a patient important information and plays a great role for a diagnosis. These intubation examinations are thus used extensively. A gastroscopic examination, in which a tube, having a diameter of a little finger, is inserted into the patient's mouth or nose, through the oesophagus and to the gastrointestinal system, is difficult to perform and demands the assistance of a physician. For the patient, the intubation of the digestive tract using these methods is a very unpleasant intervention, both physically and psychologically, especially during the insertion of the tube and also when it is pulled out. The intubation demands that the patient is given a local anaesthetic and in some instances even tranquilliser or a general anaesthetic to overcome the stress to which the patient is subjected. The incubation examination methods described above are disadvantageous since they are very time-consuming for a qualified physician and thus expensive and a very unpleasant intervention for the patient.
The application of a swallowable capsule for automatically obtaining samples of internal gastric fluids has been proposed as an alternative examination method and is described in U.S. Pat. No. 4,481,952. The capsule is equipped with mechanisms, which control the opening and closing of the capsule. The mechanisms are blocked by blocking mechanisms, including a mass which is dissolved after a short time following contact with the gastric fluid. The opening of the capsule, the collection of the sample and the reclosing of the capsule takes place automatically in the patient's stomach. The described sampling device is advantageous in many ways. However, it has proved to function unsatisfactorily and has therefore not been widely used. The described capsule is expensive, is mechanically complicated and comprises mutually movable parts, mostly metal parts. As a consequence, the parts tend to jam, fluids tend to leak between the parts, friction forces between the parts must be overcome, e.g. by spring forces, and metal parts, such as springs, may loosen in the gastrointestinal tract causing injuries to the patients.